linux-kernel - RE: [Xen-devel] [PATCH 1/2] RFC: Prepare PAD for native and xen platform

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Date:	Thu, 29 Mar 2012 07:27:47 +0000
From:	"Liu, Jinsong" <jinsong.liu@...el.com>
To:	"Liu, Jinsong" <jinsong.liu@...el.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	"Brown, Len" <len.brown@...el.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"keir.xen@...il.com" <keir.xen@...il.com>,
	Jan Beulich <jbeulich@...e.com>,
	"Li, Shaohua" <shaohua.li@...el.com>,
	"lenb@...nel.org" <lenb@...nel.org>
Subject: RE: [Xen-devel] [PATCH 1/2] RFC: Prepare PAD for native and	xen
 platform

Liu, Jinsong wrote:
> Konrad Rzeszutek Wilk wrote:
>>>> Compare approaches:
>>>> 
>>>> 1. xen overwritten approach (patches V2, x86_init, osl approach)
>>>>         Pros: a little simpler code
>>>>     Cons:
>>>>         1). specific to xen, cannot extend to other virt platform;
>>>>         2). need to change natvie acpi_pad as modular;
>>>> 
>>>> 2. paravirt interface approach (original patches V1)     Pros:
>>>>         1). standard hypervisor-agnostic interface (USENIX
>>>>         conference 2006), can easily hook to Xen/lguest/... on
>>>>         demand; 2). arch independent; 3). no need to change native
>>>>         acpi_pad as     non-modular; Cons: a little complicated
>>>> code, and code patching is some
>>>> overkilled for this case (but no harm);
>>>> 
>>>> (BTW, in the future we need add more and more pv ops, like
>>>> pv_pm_ops, pv_cpu_hotplug_ops, pv_mem_hotplug_ops, etc. So how
>>>> about add a pv_misc_ops template to handle them all? seems it's a
>>>> common issue). 
>>>> 
>> 
>> I think (and you probabaly have a better idea) is that the maintainer
>> of drivers/acpi/* is not very open to adding in code that only
>> benefits Xen.
> 
> Take paravirt interface approach as example. We only change a little
> about native acpi_pad_init/acpi_pad_exit, intercept it and
> *implicitly* hook to native/paravirt platform (it didn't appear any
> 'xen' 'pv' word in native pad logic). This is what I can find out the
> least change to native pad logic, and it in fact benefits
> (extensiable) to all pv. If this is still not acceptable we have to
> find other way (but I'm not sure) :-)      
> 
>> 
>> If it benefits other architectures (say ARM) then adding in hooks
>> there (in osl for example) makes sense - but I am not sure if ARM
>> has a form of _PUR code/calls it needs to do.
>> 
>> So with that in mind, neither of those options seems proper - as all
>> of them depend on changing something in drivers/acpi/*.
>> 
>> I've one or two suggestions of what could be done to still make this
>> work, but I need you to first see what happens if the native acpi_pad
>> runs under Xen with the latest upstream code (along with three
>> patches that are in a BZ I pointed you too).
> 
> Do you mean test the patch
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blobdiff;f=arch/x86/xen/enlighten.c;h=b132ade26f778f2cfec7c2d5c7b6db48afe424d5;hp=4172af8ceeb363d06912af15bf89e8508752b794;hb=d4c6fa73fe984e504d52f3d6bba291fd76fe49f7;hpb=aab008db8063364dc3c8ccf4981c21124866b395
> ?  

Ah, you want to test https://bugzilla.redhat.com/show_bug.cgi?id=804347
Anyway, I didn't have proper h/w platform, but seems the bug (ioapic) is irrelated to pad thread we are talking?

Thanks,
Jinsong

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